diff --git a/src/engine/fileOps.cpp b/src/engine/fileOps.cpp
index d7b515402..c2dea0085 100644
--- a/src/engine/fileOps.cpp
+++ b/src/engine/fileOps.cpp
@@ -1062,10 +1062,11 @@ bool DivEngine::loadDMF(unsigned char* file, size_t len) {
       ds.systemFlags[0].set("dpcmMode",false);
     }
 
-    // C64 no key priority and reset time
+    // C64 no key priority, reset time and multiply relative
     if (ds.system[0]==DIV_SYSTEM_C64_8580 || ds.system[0]==DIV_SYSTEM_C64_6581) {
       ds.systemFlags[0].set("keyPriority",false);
       ds.systemFlags[0].set("initResetTime",1);
+      ds.systemFlags[0].set("multiplyRel",true);
     }
 
     // OPM broken pitch
@@ -3034,11 +3035,12 @@ bool DivEngine::loadFur(unsigned char* file, size_t len) {
       }
     }
 
-    // C64 original reset time
+    // C64 original reset time and multiply relative
     if (ds.version<187) {
       for (int i=0; i<ds.systemLen; i++) {
         if (ds.system[i]==DIV_SYSTEM_C64_8580 || ds.system[i]==DIV_SYSTEM_C64_6581) {
           ds.systemFlags[i].set("initResetTime",1);
+          ds.systemFlags[i].set("multiplyRel",true);
         }
       }
     }
diff --git a/src/engine/platform/c64.cpp b/src/engine/platform/c64.cpp
index 2f25cdff0..d639fda96 100644
--- a/src/engine/platform/c64.cpp
+++ b/src/engine/platform/c64.cpp
@@ -176,7 +176,11 @@ void DivPlatformC64::tick(bool sysTick) {
       if (ins->c64.dutyIsAbs) {
         chan[i].duty=chan[i].std.duty.val;
       } else {
-        chan[i].duty-=((signed char)chan[i].std.duty.val)*4;
+        if (multiplyRel) {
+          chan[i].duty-=((signed char)chan[i].std.duty.val)*4;
+        } else {
+          chan[i].duty-=chan[i].std.duty.val;
+        }
       }
       rWrite(i*7+2,chan[i].duty&0xff);
       rWrite(i*7+3,chan[i].duty>>8);
@@ -199,10 +203,11 @@ void DivPlatformC64::tick(bool sysTick) {
       if (ins->c64.filterIsAbs) {
         filtCut=MIN(2047,chan[i].std.alg.val);
       } else {
-        // TODO:
-        // - why signed char?
-        // - add a mode in where it's not multiplied by 7 - dang it Delek
-        filtCut+=((signed char)chan[i].std.alg.val)*7;
+        if (multiplyRel) {
+          filtCut+=((signed char)chan[i].std.alg.val)*7;
+        } else {
+          filtCut+=chan[i].std.alg.val;
+        }
         if (filtCut>2047) filtCut=2047;
         if (filtCut<0) filtCut=0;
       }
@@ -726,6 +731,7 @@ void DivPlatformC64::setFlags(const DivConfig& flags) {
   }
   keyPriority=flags.getBool("keyPriority",true);
   no1EUpdate=flags.getBool("no1EUpdate",false);
+  multiplyRel=flags.getBool("multiplyRel",false);
   testAD=((flags.getInt("testAttack",0)&15)<<4)|(flags.getInt("testDecay",0)&15);
   testSR=((flags.getInt("testSustain",0)&15)<<4)|(flags.getInt("testRelease",0)&15);
   initResetTime=flags.getInt("initResetTime",2);
diff --git a/src/engine/platform/c64.h b/src/engine/platform/c64.h
index 8b69782b5..5f7882c68 100644
--- a/src/engine/platform/c64.h
+++ b/src/engine/platform/c64.h
@@ -77,7 +77,7 @@ class DivPlatformC64: public DivDispatch {
   unsigned char sidCore;
   int filtCut, resetTime, initResetTime;
 
-  bool keyPriority, sidIs6581, needInitTables, no1EUpdate;
+  bool keyPriority, sidIs6581, needInitTables, no1EUpdate, multiplyRel;
   unsigned char chanOrder[3];
   unsigned char testAD, testSR;
 
diff --git a/src/gui/insEdit.cpp b/src/gui/insEdit.cpp
index fafc3c4b6..35c7273f5 100644
--- a/src/gui/insEdit.cpp
+++ b/src/gui/insEdit.cpp
@@ -6033,8 +6033,8 @@ void FurnaceGUI::drawInsEdit() {
             if (ins->c64.dutyIsAbs) {
               dutyMax=4095;
             } else {
-              dutyMin=-96;
-              dutyMax=96;
+              dutyMin=-4095;
+              dutyMax=4095;
             }
           }
           if (ins->type==DIV_INS_STD) {
@@ -6419,8 +6419,8 @@ void FurnaceGUI::drawInsEdit() {
           }
           if (ex1Max>0) {
             if (ins->type==DIV_INS_C64) {
-              int cutoffMin=-64;
-              int cutoffMax=64;
+              int cutoffMin=-2047;
+              int cutoffMax=2047;
 
               if (ins->c64.filterIsAbs) {
                 cutoffMin=0;
diff --git a/src/gui/sysConf.cpp b/src/gui/sysConf.cpp
index 1968e1c7b..b286550ee 100644
--- a/src/gui/sysConf.cpp
+++ b/src/gui/sysConf.cpp
@@ -587,6 +587,7 @@ bool FurnaceGUI::drawSysConf(int chan, int sysPos, DivSystem type, DivConfig& fl
       int clockSel=flags.getInt("clockSel",0);
       bool keyPriority=flags.getBool("keyPriority",true);
       bool no1EUpdate=flags.getBool("no1EUpdate",false);
+      bool multiplyRel=flags.getBool("multiplyRel",false);
       int testAttack=flags.getInt("testAttack",0);
       int testDecay=flags.getInt("testDecay",0);
       int testSustain=flags.getInt("testSustain",0);
@@ -662,11 +663,17 @@ bool FurnaceGUI::drawSysConf(int chan, int sysPos, DivSystem type, DivConfig& fl
         altered=true;
       }
 
+      if (ImGui::Checkbox("Relative duty and cutoff macros are coarse (compatibility)",&multiplyRel)) {
+        altered=true;
+      }
+
+
       if (altered) {
         e->lockSave([&]() {
           flags.set("clockSel",clockSel);
           flags.set("keyPriority",keyPriority);
           flags.set("no1EUpdate",no1EUpdate);
+          flags.set("multiplyRel",multiplyRel);
           flags.set("testAttack",testAttack);
           flags.set("testDecay",testDecay);
           flags.set("testSustain",testSustain);